Disclosed herein is a vehicle seat that is capable of measuring respiration.
The physical condition of a driver is closely relevant to safe driving of a vehicle. To this end, for example, Japanese Patent Document No. 2011-156196 A (“the '196 Patent Document”) discloses a technique for monitoring a driver's physical condition by providing a device for detecting physical information such as driver's respiration in a vehicle seat.
Specifically, the '196 Patent Document discloses a biological information detection device that includes a sensor provided in a seat cushion and detects a change in a load of a seated person, and an arithmetic operation unit that computes biological information on the basis of the change in the load obtained by the sensor. This sensor is constituted by a long piezoelectric film that detects a deformation in a length direction or a bending direction. This sensor is arranged in the seat cushion a front-to-back direction which is preset so that a length direction of the sensor matches the front-to-back direction of the seat cushion over a position facing the buttocks of a seated person. This biological information detection device detects respiration or heartbeats by causing the sensor to detect the change in the load applied from the seated person, and causing the arithmetic operation unit to compute the biological information on the basis of a detected signal.
To detect a pressure change in response to the respiration right under the buttocks of the seated person, it is necessary to use a sensor capable of detecting a bending deformation such as the sensor disclosed in the '196 Patent Document. Furthermore, the load resistance performance of the sensor and the detection accuracy of the sensor are normally contradictory properties such that an improvement in one tends to diminish the other. For this reason, a load sensor detecting only the load perpendicular to a detection surface is disadvantageous in measuring a respiration signal right under the buttocks of the seated person with high accuracy.